Personal communication service (PCS) is a service in which subscribers, rather than locations or telephone stations, are assigned a personal telephone number. Calls placed to a subscriber's personal telephone number are routed to the subscriber at a telephone near that subscriber's current location. In order to provide a subscriber with such a personal communication service, e.g., as disclosed in U.S. Pat. No. 4,313,035, issued to Jordan, et al, the system providing the service (PCS system) must be supplied with the telephone number of a telephone near the subscriber's current location to which it should route calls placed to his personal telephone number. Each time the subscriber changes his location, the telephone number to which calls placed to his personal telephone number are routed must be changed. This requires the subscriber to call into the PCS system and to supply the telephone number to which his calls should currently be routed. Constantly having to call in to the PCS system can be tiresome, and supplying a ten-digit telephone number each time a subscriber changes his location is cumbersome.
To overcome these drawbacks, one prior art solution is to program a sequence of telephone numbers at any one of which the personal telephone service subscriber might be reached. The telephone numbers in a sequence are typically those of locations where a person is likely to be at various times throughout the day, such as "home," "car phone," "office," "pager," etc. When a call is made to the subscriber's personal telephone number, the PCS system attempts to complete the call by sequentially routing the call to each telephone number of the sequence. This process continues until: (a) the call is answered; (b) the call is abandoned; (c) the line associated with the telephone number is determined to be busy; or (d) until a predetermined period of time has elapsed. However, requiring the sequence of calls to be set by the subscriber in advance, and being the same for all callers, is inflexible.
Other special telephone calling systems that require a caller to enter a personal identification number (PIN) to determine to which of several potential destinations a call should be routed, are cumbersome, in that for each person a caller wishes to call, he might be required to learn a separate PIN.
Other systems exist in which calls are forwarded, or priority levels (call screening) are selected based on Automatic Number Identification (ANI). In these systems the subscriber can choose the maximum number of rings to occur at a particular location, or tailor the response of an answering machine based on the ANI. Other similar systems are described in U.S. Pat. Nos. 5,199,062 and 5,239,577.
Another related patent of interest is U.S. Pat. No. 5,430,791, which patent is assigned to the same assignee as is the instant application.
However, none of the prior art systems give the calling party the flexibility of specifically providing caller directive announcements which indicate the location or status of the subscriber.